Jordan Vlahos, 6, sitting in class at Sun Valley Elementary School in San Rafael, wiggled in his chair – or rather, what would have been his chair, except that he was sitting on a balance ball.

The 23 kindergartners in Ally Mitchell’s class at Sun Valley sit on bright green plastic globes variously known as stability balls or balance balls. Children need to move to focus during complicated mental tasks, a 2008 University of Central Florida study suggests.

“Some kids need more wiggle time,” Mitchell said. “So I got a stability ball. Soon all the kids wanted to sit on the wiggle chair. They loved it. I thought, ‘Why not let everyone do it?'”

In Mitchell’s class Thursday, some children were sitting with their legs apart, effortlessly keeping upright, while others sat with feet together, close to the round tables where they were working.

“When they leave the table, they push the balls under the table,” Mitchell said. “Conventional chairs don’t go under the table, so the balls leave more room.” Five short legs stick out of each ball, anchoring it so it won’t roll when unused.

“They’re squishy,” Jordan said. “I can wiggle like this,” he said, illustrating with a side-to-side motion, “and I can bounce. But not too high.”

Mitchell said, “I taught them explicitly how to sit on one. If they bounce too high and don’t have two feet on the floor, they get a quiet warning. The next time, they have to sit in a regular chair.”

The balls don’t offer back support, but Mitchell said that’s not an issue because they help develop core strength.

Because the chair is round and tends to roll, the body instinctively engages core muscle groups such as the abs. Constant movement, however slight, is required to stay seated, and this helps people, particularly children, to focus — keeping on the ball, so to speak.

The students “are all obeying the rules,” the teacher said. One student hit his chair with a pencil and popped it, she said.

“It was a life lesson. He cried,” Mitchell said. “If you break something, you are responsible for it.” After consulting with the boy’s parents, the teacher arranged for him to pay for a new ball from his piggy bank.

In addition to the 2008 study, a 2007 study by the Mayo Clinic in Rochester on the benefits of a chairless classroom found that the ability to move around while sitting made students more attentive.

Some classrooms, including a fourth-grade classroom at Vallecito Elementary School in San Rafael, use standing desks. These, too, are effective in helping students be less sedentary. Those desks cost around $250, however; the balance chairs cost $20 apiece and were paid for by a teacher grant from the San Rafael Rotary Club.

The class has had the chairs about a month, Mitchell said.

“It’s something so simple, but it makes a big difference,” said Sun Valley Principal Julie Harris. “In combination with all the practices we have at our school, including mindfulness training, it helps to make students more engaged learners.”

Harris said many tech companies, including Google, have innovative furniture design. The chairs fall into that category, she said.

“The thinking is, ‘How do we allow our employees to be creative?'” Harris said. “Like Google, we’re thinking about how we can help children move, instead of forcing everybody to be seated for six hours a day, like in the olden days.”

Jordan Vlahos, 6, sitting in class at Sun Valley Elementary School in San Rafael, wiggled in his chair – or rather, what would have been his chair, except that he was sitting on a balance ball.

The 23 kindergartners in Ally Mitchell’s class at Sun Valley sit on bright green plastic globes variously known as stability balls or balance balls. Children need to move to focus during complicated mental tasks, a 2008 University of Central Florida study suggests.

“Some kids need more wiggle time,” Mitchell said. “So I got a stability ball. Soon all the kids wanted to sit on the wiggle chair. They loved it. I thought, ‘Why not let everyone do it?'”

In Mitchell’s class Thursday, some children were sitting with their legs apart, effortlessly keeping upright, while others sat with feet together, close to the round tables where they were working.

“When they leave the table, they push the balls under the table,” Mitchell said. “Conventional chairs don’t go under the table, so the balls leave more room.” Five short legs stick out of each ball, anchoring it so it won’t roll when unused.

“They’re squishy,” Jordan said. “I can wiggle like this,” he said, illustrating with a side-to-side motion, “and I can bounce. But not too high.”

Mitchell said, “I taught them explicitly how to sit on one. If they bounce too high and don’t have two feet on the floor, they get a quiet warning. The next time, they have to sit in a regular chair.”

The balls don’t offer back support, but Mitchell said that’s not an issue because they help develop core strength.

Because the chair is round and tends to roll, the body instinctively engages core muscle groups such as the abs. Constant movement, however slight, is required to stay seated, and this helps people, particularly children, to focus — keeping on the ball, so to speak.

The students “are all obeying the rules,” the teacher said. One student hit his chair with a pencil and popped it, she said.

“It was a life lesson. He cried,” Mitchell said. “If you break something, you are responsible for it.” After consulting with the boy’s parents, the teacher arranged for him to pay for a new ball from his piggy bank.

In addition to the 2008 study, a 2007 study by the Mayo Clinic in Rochester on the benefits of a chairless classroom found that the ability to move around while sitting made students more attentive.

Some classrooms, including a fourth-grade classroom at Vallecito Elementary School in San Rafael, use standing desks. These, too, are effective in helping students be less sedentary. Those desks cost around $250, however; the balance chairs cost $20 apiece and were paid for by a teacher grant from the San Rafael Rotary Club.

The class has had the chairs about a month, Mitchell said.

“It’s something so simple, but it makes a big difference,” said Sun Valley Principal Julie Harris. “In combination with all the practices we have at our school, including mindfulness training, it helps to make students more engaged learners.”

Harris said many tech companies, including Google, have innovative furniture design. The chairs fall into that category, she said.

“The thinking is, ‘How do we allow our employees to be creative?'” Harris said. “Like Google, we’re thinking about how we can help children move, instead of forcing everybody to be seated for six hours a day, like in the olden days.”